Wind turbine blades of fibre-reinforced polymer and in particular the aerodynamic shells of wind turbine blades are usually manufactured in moulds, where the pressure side and the suction side of the blade are manufactured separately by arranging glass fibre mats in each of the two mould parts. Then, the two halves are glued together, often by means of internal flange parts. Glue is applied to the inner face of the lower blade half before the upper blade half is lowered thereon. Additionally, one or two reinforcing profiles (beams) are often attached to the inside of the lower blade half prior to gluing to the upper blade half.
The aerodynamic shell parts are typically made by use of Vacuum Assisted Resin Transfer Moulding (VARTM), where a plurality of fibre mats are arranged on top of a rigid mould parts and possibly also a core material to provide parts having a sandwich structure. When the fibre mats have been stacked and overlapped so as to form the final shape of the wind turbine blade shell part. Then a flexible vacuum bag is arranged on top of the fibre mats and sealed against the rigid mould part, thereby forming a mould cavity containing the fibre mats. Resin inlets and vacuum outlets are connected to the mould cavity. First the mould cavity is evacuated via the vacuum outlets so as to form an underpressure in the mould cavity, after which a supply of liquid resin is supplied via the resin inlets. The resin is forced into the mould cavity due to the pressure differential and impregnates the fibre material of the fibre mats. When the fibre material has been fully impregnated, the resin is cured in order to form the final composite structure, i.e. the wind turbine shell part.
Many of the above processes including the layout of the fibre mats are usually carried out manually.
Wind turbine blades have become increasingly longer of the years and blades having a length of more than 70 meters are now commercially available on the market. This also means that larger moulds have to be used. Due to the large size, it has become increasingly complicated to lay out the fibre mats and further to obtain proper wetting of the fibre material. None the less, many of the different processes are still carried out manually, which increases the risk of errors occurring, such as formation of wrinkles in the fibre material or areas of insufficient wetting of the fibre material, which in turn can be detrimental to the mechanical strength of the composite structure and may necessitate that the manufactured wind turbine blade shell part has to scrapped. Further, the cycle time for each process, i.e. laying up fibre material, impregnating the fibre material and curing the resin to form the final product, all increase.